Many copper alloys have poor intermediate temperature range (i.e., between about 300.degree. and about 700.degree. C.) tensile ductility which may lead to premature failure in service or to reheat cracking following welding. General recognition of such shortcomings has stimulated attempts by others to solve the problem with the result that various alloys have been developed to optimize strength and ductility properties. In one such instance directed to cast copper alloys for marine applications, where repair welding without reheat cracking is vitally important, the optimized copper-base alloy contained 13% nickel, 2% iron, 5% manganese and 3% aluminum. That alloy, however, may not prove to be a satisfactory answer to the problem for although the manganese addition improves the high strain rate hot ductility of the alloy, it does so at the expense of room temperature strength. Also, the intermediate temperature range tensile ductility is still very poor which may limit weldability. In addition, other copper-nickel alloys, for example, for condenser tube use in which reliability depends importantly upon both strength and ductility, may not always meet the needs of plant designers.